129281728 has 14 divisors (see below), whose sum is σ = 256543556. Its totient is φ = 64640832.

The previous prime is 129281723. The next prime is 129281729. The reversal of 129281728 is 827182921.

It is a super-3 number, since 3×129281728³ (a number of 25 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (129281723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1009950 + ... + 1010077.

Almost surely, 2^129281728 is an apocalyptic number.

It is an amenable number.

129281728 is a deficient number, since it is larger than the sum of its proper divisors (127261828).

129281728 is an equidigital number, since it uses as much as digits as its factorization.

129281728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2020039 (or 2020029 counting only the distinct ones).

The product of its digits is 32256, while the sum is 40.

The square root of 129281728 is about 11370.2123111224. The cubic root of 129281728 is about 505.6449987990.

The spelling of 129281728 in words is "one hundred twenty-nine million, two hundred eighty-one thousand, seven hundred twenty-eight".